Brake rotor assembly

ABSTRACT

A brake rotor assembly, and method for forming a brake rotor assembly, that includes an integrally formed first disc member coupled to an integrally formed second disc member, wherein a first portion of the outer surface of the first disc member and the second disc member is formed from a metal matrix composite and the remainder of the first disc member and second disc member is formed from the support element used in the first portion.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/573,334 filed Sep. 2, 2011, the disclosures ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention generally relates to a brake rotor assembly for avehicle.

2. Description of the Prior Art

Metal matrix composites (MMCs) are composite materials that comprise atleast two constituents, one being a primary metal and the other being adifferent secondary metal or another material, such as a ceramic articleor organic compound. As compared to monolithic materials comprising asingle constituent, MMCs have a higher strength-to-density ratio, ahigher stiffness-to-density ratio, and higher strength at elevatedtemperatures. MMCs also have a higher wear resistance than monolithicmaterials. As such, MMCs are typically useful for applications requiringwear resistance and strength, e.g., brakes. More specifically, MMCsprovide higher/better wear resistance when utilized in brakes and thusextends the life of brakes. For a further discussion of MMCs, see U.S.Pat. No. 7,793,703, U.S. Pat. No. 8,016,018 and U.S. Patent ApplicationPublication No. 2009/0312174 which are herein incorporated by reference.

MMCs are produced by augmenting the primary metal with the secondarymetal or other material, which are typically some type of reinforcingmaterial. The metals used for the primary metal and the reinforcingmaterial are typically chosen to optimize the desired mechanical andphysical properties of the MMCs. Numerous combinations of metals andreinforcing materials are known in the art. Examples of an effectivemetal as the primary metal are aluminum, magnesium, titanium, copper,zinc, and superalloys. Examples of effective reinforcing materialscomprise boron carbide, silicon carbide, alumina, and graphite, and areavailable in the form of continuous fibers, discontinuous fibers,particles, and whiskers.

SUMMARY OF THE INVENTION AND ADVANTAGES

The present invention provides a brake rotor assembly comprising:

a first disc member having an inner disc surface and an outer discsurface and comprising:

-   -   a first preform comprising ceramic particles and ceramic fibers        with said first preform having an inner surface and an opposing        outer surface and defining a plurality of voids;    -   a first support element comprising a metal, a first portion of        said first support element disposed within said plurality of        voids of said first perform between said inner surface and said        opposing outer surface of said first preform for forming a metal        matrix composite with said first support element terminating at        said outer surface of said first preform such that said opposing        outer surface of said first preform remains exposed;    -   said first support element further comprising a backing portion        extending from said inner surface of said first preform, said        backing portion of said first support element defining at least        a portion of said outer disc surface of said first disc member;    -   a first wear surface defined by said exposed outer surface and        by said first portion of said first support element, said first        wear surface defining a portion of said outer disc surface of        said first disc member; and    -   (b) a second disc member coupled to said first disc member, said        second disc member having an inner disc surface and an outer        disc surface and comprising:    -   a second preform comprising ceramic particles and ceramic fibers        with said second preform having an inner surface and an opposing        outer surface and defining a plurality of voids;    -   a second support element comprising said metal, a first portion        of said second support element disposed within said plurality of        voids of said second perform between said inner surface and said        opposing outer surface of said second preform for forming a        metal matrix composite with said second support element        terminating at said opposing outer surface of said second        preform such that said opposing outer surface of said second        preform remains exposed;    -   said second support element further comprising a backing portion        extending from said inner surface of said first preform, said        backing portion of said second support element defining at least        a portion of said outer disc surface of said second disc member;    -   a second wear surface defined by said exposed outer surface and        by said first portion of said second support element, said        second wear surface defining a portion of said outer disc        surface of said second disc member;    -   wherein said backing portion of each of said first support        element and said second support element are located between said        first wear surface and said second wear surface when said first        disc member is coupled to said second disc member and    -   wherein said inner disc surface of said first disc member is        spaced apart from said second disc member when said first disc        member is coupled to said second disc member.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will be readily appreciated, as thesame becomes better understood by reference to the following detaileddescription, when considered in connection with the accompanyingdrawings.

FIG. 1 is a perspective view of a brake rotor assembly according to oneexemplary embodiment.

FIG. 1A is a close-up view of a portion of the brake rotor assembly ofFIG. 1.

FIG. 1B is a section view of the brake rotor assembly taken along line1B-1B.

FIG. 2 is a rear view of the brake rotor assembly of FIG. 1.

FIG. 3 is an exploded view of the brake rotor assembly of FIG. 1.

FIG. 4 is another exploded view of the brake rotor assembly of FIG. 1.

FIG. 5 is a perspective view of a brake rotor assembly according to asecond embodiment.

FIG. 6 is an enlarged view of a block of FIG. 5.

FIG. 7 is an enlarged view of the base portion and the post of FIG. 5.

FIG. 8 is a partially exploded view of a nut aligning with the post andthe post disposed in a slot of the block of the brake rotor assembly ofFIG. 5.

FIG. 9 is a perspective view of a brake rotor assembly of a thirdembodiment.

FIG. 10 is an enlarged perspective view of a plug disposed in a firstand second opening of a first and second ear according to the brakerotor assembly of FIG. 9.

FIG. 11 is a perspective view of the plug of the brake rotor assembly ofFIG. 9.

FIG. 12 is an exploded view of the plug, first ear and second ear of thebrake rotor assembly of FIG. 9.

FIG. 13 is a perspective view of a brake rotor assembly according toanother exemplary embodiment.

FIG. 14 is a perspective view of a brake rotor assembly according to yetanother exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures, wherein like numerals indicate like orcorresponding parts throughout the several views, a brake rotor assembly20 for a vehicle (not shown) is generally shown. Generally, the brakerotor assembly 20 is utilized with a caliper mechanism for braking orslowing the vehicle as known to those skilled in the art. It is to beappreciated that the brake rotor assembly 20 can be utilized with anysuitable mechanism for braking the vehicle. It is also to be appreciatedthat the vehicle can be a heavy duty type of vehicle, such as a heavyduty truck, etc., a light type of vehicle, such as a car, etc., or anyother type of vehicle utilizing a brake system.

Referring to FIGS. 1-4, the brake rotor assembly 20 in accordance withone exemplary embodiment is shown and includes a first disc member 22and a second disc member 24 coupled to each other. Each disc member 22,24 include an inner disc surface 23 and an outer disc surface 25, andthus when the disc members 22, 24 are coupled the inner disc surfaces 23are located between the outer disc surfaces 25 in such a way that thereis a gap 29 defined between the inner disc surfaces 23 (i.e. the innerdisc surfaces 23 do not abut one another). More specifically, the firstand second disc members 22, 24 are attached (i.e. mechanically fastened)to each other as further discussed below.

The first and second disc members 22, 24 each include a first portion 26and a second portion 28. The first and second portions 26, 28 of thefirst disc member 22 are adjacent each other, and likewise, the firstand second portions 26, 28 of the second disc member 24 are adjacenteach other. For illustrative purposes only, various Figures show animaginary line to help illustrate and distinguish the first portion 26from the second portions 28. The composition of the first portion 26 andof the second portion 28 of each respective disc 22, 24 will bedescribed in further detail below.

The first and second disc members 22, 24 each define an aperture 30along a central axis C.

In certain embodiments, as best shown in FIGS. 1 and 2, the firstportion 26 of the first disc member 22 is spaced from the aperture 30 ofthe first disc member 22 and the second portion 28 of the first discmember 22 is adjacent the aperture 30 of the first disc member 22, whileboth the first portion 26 and second portion 28 extend to the outerperiphery 32. In other words, an radially inward portion 128 of thesecond portion 28 of the first disc member 22 is disposed between theaperture 30 and the inner periphery 126 of the first portion 26 of thefirst disc member 22 radially relative to the central axis C and extendsbetween the inner disc surface 23 and the outer disc surface 25, while abacking portion 228 of the second portion 28 is disposed radiallyoutward from the inner portion 128 and is located adjacent to the firstportion 26 and extends to the outer periphery 32 of the disc member 22.In this embodiment, the radially inward portion 128 and backing portion228 together define the inner disc surface 23 of the first disc member22.

Likewise, the first portion 26 of the second disc member 24 is spacedfrom the aperture 30 of the second disc member 24 and the second portion28 of the second disc member 24 is adjacent the aperture 30 of thesecond disc member 24. In other words, a radially inward portion 128 ofthe second portion 28 of the second disc member 24 is disposed betweenthe aperture 30 and the inner periphery 126 of the first portion 26 ofthe second disc member 24 radially relative to the central axis C andextends between the inner disc surface 23 and the outer disc surface 25,while a backing portion 228 of the second portion 28 is disposedradially outward from the inner portion 128 and is located adjacent tothe first portion 26 and extends to the outer periphery 32 of the seconddisc member 24. In this embodiment, the radially inward portion 128 andbacking portion 228 together define the inner disc surface 23 of thesecond disc member 24.

Alternatively, in other embodiments (not shown), the first portion 26and the second portion 28 each abut the outer periphery 32 and theaperture 30. In this embodiment, the first portion 26 defines the outerdisc surface 25 of the respective disc members 22, 24, while the secondportion 28 defines the inner disc surface 23 of the respective discmembers 22, 24. Stated differently, the second portion 28 defines abacking portion 228 that extends from the inner periphery 126 and outerperiphery 32 and defines the entirety of the inner disc surface 23.

In certain embodiments, as best shown in FIGS. 1, 2, 3, and 4 the firstdisc member 22 includes a plurality of fins 36 extending outwardly alongthe central axis C. More specifically, the fins 36 extend outwardly fromthe second portion 28 of the first disc member 22, and even morespecifically from the backing portion 228 of the first disc member 22,toward the second disc member 24 radially relative to the central axisC. The fins 36 abut the second disc member 24 such that the inner discsurface 23 of the first disc member 22 is spaced from the inner discsurface 23 of the second disc member 24. The fins 36 aid in cooling thefirst and second disc members 22, 24.

It is to be appreciated that the fins 36 can extend from the second discmember 24 instead of the first disc member 22, or the fins 36 can extendfrom the second disc member 24 in addition to the fins 36 extending fromthe first disc member 22.

In certain embodiments, such as shown in FIGS. 1, 2, 3 and 4, the firstdisc member 22 includes a plurality of fingers 38 extending outwardlyalong the central axis C. More specifically, the fingers 38 extendoutwardly toward the second disc member 24 and additionally, the fingers38 are disposed adjacent the aperture 30 of the first disc member 22.Even more specifically, the fingers 38 extend from the second portion 28of the first disc member 22. Even more specifically, the fingers 38extend from the radially inward portion 128 of the first disc member 22.In alternative embodiments not shown, wherein the backing member 228extends from the inner periphery 126 to the outer periphery 32 (i.e.wherein there is no radially inward portion 128), the fingers 38 mayextend from the backing member 228. Generally, the fingers 38 and thefins 36 extend along the central axis C in the same direction and thefingers 38 are spaced from the fins 36. It is to be appreciated that thefingers 38 and the fins 36 can abut each other. For example, the fingers38 and the fins 36 can be blended together where the fingers 38 and fins36 meet. It is to further be appreciated that the fingers 38 can be anysuitable configuration and orientation.

As best shown in FIG. 2, the second disc member 24 includes a flange 40extending outwardly along and transverse to the central axis C such thatthe aperture 30 of the second disc member 24 defines a first diameterand a second diameter less than the first diameter. More specifically,the flange 40 extends from the second portion 28 of the second discmember 24. Even more specifically, the flange 40 extends from theradially inward portion 128 of the first disc member 22. In alternativeembodiments not shown, wherein the backing member 228 extends from theinner periphery 126 to the outer periphery 32 (i.e. wherein there is noradially inward portion 128), the flange 40 may extend from the backingmember 228. The aperture 30 of the first disc member 22 complements thefirst diameter of the aperture 30 of the second disc member 24. It is tobe appreciated that the flange 40 can be any suitable configuration andorientation.

The second disc member 24 defines a plurality of recesses 42 extendingalong the central axis C and spaced from each other. More specifically,the recesses 42 extend along the central axis C away from the first discmember 22. The recesses 42 are adjacent the aperture 30 of the seconddisc member 24, and more specifically, the recesses 42 are adjacent theaperture 30 defining the first diameter. Even more specifically, thesecond portion 28 of the second disc member 24 defines the recesses 42.Even more specifically, the radially inward portion 128 of the seconddisc member 24 defines the recesses 42. In alternative embodiments notshown, wherein the backing member 228 extends from the inner periphery126 to the outer periphery 32 (i.e. wherein there is no radially inwardportion 128), the backing member 228 defines the recesses 42. Thefingers 38 and the recesses 42 align with each other; as such, thefingers 38 are disposed in the recesses 42 for keying the first andsecond disc members 22, 24 together. Further, the fingers 38 and therecesses 42 engage each other for preventing slippage of the first andsecond disc members 22, 24 relative to each other. The recesses 42 canbe any suitable configuration and orientation complementary to thefingers 38.

The second portion 28 of each of the first and second disc members 22,24 define a plurality of holes 44. Even more specifically, the radiallyinward portion 128 each of the first and second disc members 22, 24defines the recesses 42. In alternative embodiments not shown, whereinthe backing member 228 extends from the inner periphery 126 to the outerperiphery 32 (i.e. wherein there is no radially inward portion 128), thebacking member 228 of each of the first and second disc members 22, 24defines the recesses 42. The holes 44 of the first disc member 22 alignwith the holes 44 of the second disc member 24. In other words, one hole44 of the first disc member 22 aligns with one hole 44 of the seconddisc member 24, etc. The holes 44 of the first disc member 22 are spacedfrom the inner periphery 34 and the first portion 26 of the first discmember 22. Likewise, the holes 44 of the second disc member 24 arespaced from the inner periphery 34 and the first portion 26 of thesecond disc member 24. Further, the holes 44 of the first disc member 22are spaced from the fingers 38 and the holes 44 of the second discmember 24 are spaced from the recesses 42. It is to be appreciated thatthe holes 44 of the first disc member 22 can be through holes and theholes 44 of the second disc member 24 can be blind holes. It is tofurther be appreciated that the holes 44 of the second disc member 24can be through holes.

The brake rotor assembly 20 further includes a plurality of pins 46disposed in the holes 44 of the first and second disc members 22, 24.Specifically, one pin 46 is disposed in one hole 44 of the first andsecond disc members 22, 24 and another pin 46 is disposed in anotherhole 44 of the first and second disc members 22, 24, etc. The pins 46secure together the first and second disc members 22, 24. In oneembodiment, the pins 46 are further defined as bolts. It is to beappreciated that the pins 46 can be further defined as threaded pins,threaded bolts, screws, press-fit pins, interference-fit pins, etc. orany other suitable fastener. The pins 46 are recessed in the holes 44 ofthe first disc member 22 for preventing the pins 46 from being exposedto various components. When the holes 44 of the second disc member 24are through holes, the pins 46 can also be recessed in the holes 44 ofthe second disc member 24 for preventing the pins 46 from being exposedto various components. It is to be appreciated that the holes 44 of thefirst and second disc members 22, 24 and the pins 46 can be any suitableconfiguration for cooperating with each other.

Therefore, the fingers 38, the recesses 42, the holes 44, and the pins46 cooperate to secure the first and second disc members 22, 24 togetherand prevent separation of the first and second disc members 22, 24. Inother words, the fingers 38, the recesses 42, the holes 44, and the pins46 cooperate to mechanical fasten the first and second disc members 22,24 together. When, for example, the caliper mechanism engages the firstand second disc members 22, 24, a force is applied to the first andsecond disc members 22, 24, which further pushes or tightens the discmembers 22, 24 together.

The brake rotor assembly 20 also provides alternative embodiments forthe first and second disc members 22, 24 that are substantially similarto FIGS. 1-4.

For example, as shown in FIG. 13, an alternative brake rotor assembly 20is illustrated in which the fins 36 are removed and the overall mass ofthe discs 22, 24 is increased relative to FIGS. 1-4. In this embodiment,cooling of the disc member 22 is enhanced through the introduction ofone or more grooves 501 into the outer disc surface 25, and morespecifically into the wear surface 125 of the first portion 26 of thedisc 22. These one or more grooves 501 may be incorporated into thedesign during the forming process or may be cut into the wear surface125 in a post production step. In addition, the outer surface 25 of theradially inward portion 128 of the second portion 28 may be taperedinward towards the second disc member 24 and include a plurality ofnotches, or slots 503. The slots 503 further aid in cooling the firstdisc member 22 during use.

As shown in FIG. 14, another alternative brake rotor assembly 20 isillustrated in which the fins 36 are maintained and the overall mass ofthe discs 22, 24 is increased relative to FIGS. 1-4. Here, as in FIG.13, the outer surface 25 of the radially inward portion 128 of thesecond portion 28 may be tapered inward towards the second disc member24 and include a plurality of notches, or slots 503. The slots 503further aid in cooling the first disc member 22 during use.

The brake rotor assembly 20 also provides alternative embodiments formechanically fastening the first and second disc members 22, 24together. For example, FIGS. 5-8 provide a second embodiment and FIGS.9-12 provide a third embodiment. Each of these embodiments will bediscussed below. All of the features discussed above having commonreference numbers apply to the second and third embodiments except asset forth below.

With regard to FIGS. 5-8, the first disc member 22 includes a pluralityof blocks 48 spaced from each other radially relative to the centralaxis C with each of the blocks 48 define a slot 50. The blocks 48 extendfrom the second portion 28 of the first disc member 22, and morespecifically, the blocks 48 are disposed adjacent the outer periphery 32of the first disc member 22. In certain embodiments, the blocks areintegrally formed with the second portion 28 of the first disc member22.

The second disc member 24 includes a plurality of bases 52 spaced fromeach other radially relative to the central axis C. More specifically,the bases 52 extend from the second portion 28 of the second disc member24. In certain embodiments, the bases 52 are integrally formed with thesecond portion 28 of the second disc member 24. One base 52 is disposedadjacent one block 48, etc. It is to be appreciated that the bases 52and the blocks 48 can abut each other or be spaced from each other.

Each of the bases 52 includes a post 54 extending transverse to thecentral axis C. The posts 54 and the blocks 48 secure together the firstand second disc members 22, 24. Specifically, the posts 54 complementthe slots 50 of the blocks 48 such that one post 54 is disposed in oneslot 50 and another post 54 is disposed in another slot 50, etc.Further, one block 48, one base 52, and one post 54 is disposed betweena pair of fins 36 and another block 48, another base 52, and anotherpost 54 is disposed between another pair of fins 36, etc. The bases, andthus the posts 54, are disposed adjacent the outer periphery 32 of thesecond disc member 24. Having the posts 54 and the blocks 48 adjacentthe outer periphery 32 prevents bending or flexing of the first andsecond disc members 22, 24.

A plurality of nuts 56 are secured the posts 54 for securing the posts54 to the blocks 48 and thus securing the first and second disc members22, 24 together. Specifically, one nut 56 is secured to an end of onepost 54 and another nut 56 is secured to an end of another post 54, etc.The nuts 56 can be further defined as a threaded nuts 56, press-fit nuts56, etc. The nuts 56 are recessed in the slots 50 of the blocks 48 forpreventing the nuts 56 from being exposed to various components.Further, the posts 54 are recessed in the slots 50 of the blocks 48 forpreventing the posts 54 from being exposed to various components.

Therefore, the blocks 48, the slots 50, the bases 52, the posts 54, andthe nuts 56 cooperate to secure the first and second disc members 22, 24together and prevent separation of the first and second disc members 22,24. In other words, the blocks 48, the slots 50, the bases 52, the posts54, and the nuts 56 cooperate to mechanical fasten the first and seconddisc members 22, 24 together. As such, the blocks 48, the slots 50, thebases 52, the posts 54, and the nuts 56 can be any suitableconfiguration and orientation for cooperating with each other.

The first disc member 22 of this embodiment also includes the fingers 38and the second disc member 24 of this embodiment includes the recesses42 as also discussed above. Further, the first disc member 22 includesthe fins 36 and the second disc member 24 includes the flange 40 asdiscussed above. In other words, the first and second disc members 22,24 of this embodiment as shown in FIGS. 5-8 are different from the firstand second disc members 22, 24 of the embodiment illustrated in FIGS.1-4, as discussed above, in that the holes 44 and pins 46 are eliminatedand replaced with the blocks 48, bases 52 and nuts 56 that are use tocouple the discs 22, 24 together.

With regard to FIGS. 9-12, the first disc member 22 includes a pluralityof first ears 58 spaced from each other radially relative to the centralaxis C. More specifically, the first ears 58 extend from the secondportion 28 of the first disc member 22. Even more specifically, thefirst ears 58 extend from, and may be integrally formed as a part of,the backing portion 228 of the first disc member 22. Each of the firstears 58 define a first opening 60 transverse to the central axis C.Likewise, the second disc member 24 includes a plurality of second ears62 spaced from each other radially relative to the central axis C. Morespecifically, the second ears 62 extend from the second portion 28 ofthe second disc member 24. Even more specifically, the second ears 62extend from, and may be integrally formed as a part of, the backingportion 228 of the second disc member 24. Each of the second ears 62defines a second opening 61 transverse to the central axis C. The firstand second ears 58, 62 cooperate with each other such that the first 60and second openings 61 align. As such, one first ear 58 is disposedadjacent one second ear 62, etc. In certain embodiments, such as shownin FIGS. 9-12, the second ear 62 is spaced radially outwardly from theaperture 30 relative to the first ear 58, however, in alternativeembodiments (not shown), it is contemplated that the first ear 58 may bespaced radially outwardly relative to the aperture 30 relative to thesecond ear 62. It is to be appreciated that the first and second ears58, 62 can abut each other or be spaced from each other. The first ears58 are adjacent the outer periphery 32 of the first disc member 22 andthe second ears 62 are adjacent the outer periphery 32 of the seconddisc member 24. Further, one first ear 58 and one second ear 62 isdisposed between a pair of fins 36 and another first ear 58 and anothersecond ear 62 is disposed between another pair of fins 36, etc. Havingthe first and second ears 58, 62 adjacent the outer periphery 32prevents bending or flexing of the first and second disc members 22, 24.It is to be appreciated that the first and second ears 58, 62, as wellas the first 60 and second openings 61, can be any suitableconfiguration and orientation.

A plurality of plugs 66 are disposed in the first 60 and second openings61 for securing the first and second ears 58, 62 to each other, and thussecuring the first and second disc members 22, 24 together.Specifically, one plug 66 is disposed in one of the first 60 and secondopenings 61 and another plug 66 is disposed in another one of the first60 and second openings 61. The plugs 66 can be further defined as wedges68 as shown in FIG. 11. The wedges 68 include at least one side 70having a tapered surface 72, and more specifically, two sides 70 havingthe tapered surface 72. The wedges 68 are wedged into the first 60 andsecond openings 61 for securing the first and second ears 58, 62together, and thus securing the first and second disc members 22, 24together. As such, the wedges 68 provide an interference fit. It is tobe appreciated that the plugs 66 can provide an interference-fit or afriction fit, a press-fit, etc. It is to further be appreciated that theplugs 66 can be any suitable configuration and orientation.

Therefore, the first and second ears 58, 62, the first 60 and secondopenings 61, and the plugs 66 cooperate to secure the first and seconddisc members 22, 24 together and prevent separation of the first andsecond disc members 22, 24. In other words, the first and second ears58, 62, the first 60 and second openings 61, and the plugs 66 cooperateto mechanical fasten the first and second disc members 22, 24 together.As such, the first and second ears 58, 62, the first 60 and secondopenings 61, and the plugs 66 can be any suitable configuration andorientation for cooperating with each other.

The first disc member 22 of the embodiment illustrated in FIGS. 9-12also includes the fingers 38 and the second disc member 24 of thisembodiment includes the recesses 42 as also discussed above in FIGS. 1-4and 5-7. Further, the first disc member 22 includes the fins 36 and thesecond disc member 24 includes the flange 40 as discussed above. Inother words, the first and second disc members 22, 24 of this embodimentare different from the first and second disc members 22, 24 of the firstembodiment as discussed above in that the holes 44 and pins 46 areeliminated in this embodiment. In addition, the first and second discmembers 22, 24 of the embodiment of FIGS. 9-12 are different from thefirst and second disc members 22, 24 of the embodiment of FIGS. 5-7 asdiscussed above in that the blocks 48, the slots 50, the bases 52, theposts 54, and the nuts 56 are eliminated in this embodiment.

In each of the embodiments, as noted above, the discs 22, 24 include afirst portion 26 and a second portion 28. Generally, the calipermechanism includes brake pads that face the outer disc surface 25, andmore specifically faces the first portion 26 of the respective discs 22,24. As such, when the brake pads engage the discs 22, 24, they engage aportion of the outer disc surface 25, and more specifically a wearsurface 125 of the first portion 26 of each of the discs 22, 24, andsuch engagement by the brake pads acts to slow down the vehicle.

Given this engagement with the brake pads, as represented herein withrespect to the embodiment as shown in FIGS. 1-4 and specifically toFIGS. 1A and 1B, but applicable to the embodiments of FIGS. 5-8 and 9-12and 13 and 14, the wear surface 125 of the first portion 26 should bedurable and wear resistant at elevated temperatures normally encounteredduring braking in vehicles such as cars, trucks, or other heavy dutyequipment. The second portion 28 of each of the discs 22, 24, as opposedto the wear surface 125 of the first portion 26, does not engage thebrake pads to slow the vehicle and therefore does not require the samestrength and wear resistant properties at elevated temperatures as thefirst portion 26. However, it is desirable that the material utilized inthe second portion 28 have mechanical and physical properties that workin conjunction with the materials of the first portion 26 to enhance theductility to the overall discs 22, 24, as well as maximizing the thermalproperties for the discs 22, 24.

In addition, it is highly desirable that the first and second portions26, 28 of each respective discs 22, 24 are formed as an integratedobject that maximizes each of the characteristics described above (i.e.the discs 22, 24 are “integrally formed”). Stated differently, it ishighly desirable that the first portion 26 and second portion 28 are notformed individually and then secondarily fused, laminated or otherwisecoupled to form the respective first and second disc members 22, 24.

In order to achieve these desired characteristics, in each ofembodiments of the present invention as described above, and as shownherein best in FIGS. 1A and 1B the first portion 26 of each of theintegrally formed respective discs 22, 24, including the afore-mentionedwear surface 125, that engages the brake pads is a metal matrixcomposite (MMC) that includes a preform 200 formed from a compositionhaving ceramic particles and ceramic fiber impregnated or infiltratedwith a support element 250 formed from a metal that fills the pluralityof voids 275 within the preform 200.

The second portion 28 is formed of the same support element 250 thatinfiltrates or impregnates the preform 200 to form the MMC first portion26. Stated differently, the support element 250 of the second portion 28is formed from the same metal that is utilized in the first portion 26.

Suitable metals that may be used as the support element 250 include,pure metals or metal alloys, including, for example, pure aluminum oraluminum alloys. It is to be appreciated that the pure metals, such aspure aluminum, can further be defined as metal substantially free ofimpurities.

The ceramic fibers used in the preform 200 typically comprise an elementfrom period 2, 3, 4, or 5 of the periodic table of the elements.Typically, the ceramic fibers comprise aluminum, silicon, oxygen,zirconium, or carbon. The ceramic fibers are typically selected from thegroup of alumina-silica fibers, alumina-silica-zirconia fibers,carbon-graphite fibers, and combinations thereof. Carbon-graphite fibersare typically selected for applications requiring high strength.

In one embodiment, the ceramic fibers have an aspect ratio of greaterthan 3:1. In another embodiment, the ceramic fibers have an aspect ratioof greater than or equal to 5:1. In yet another embodiment, the ceramicfibers have an aspect ratio of greater than or equal to 10:1. It is tobe appreciated that the term aspect ratio means a ratio of the longerdimension, i.e., length, of the ceramic fibers to the shorter dimension,i.e., diameter, of the ceramic fibers. The ceramic fibers typically havea length of from 5 to 500 μm, more typically from 50 to 250 μm. Theceramic fibers typically have a diameter of from 1 to 20 μm, moretypically from 2 to 5 μm. Without intending to be limited by theory, itis believed that ceramic fibers having an aspect ratio of greater than3:1 decrease the density of the preform 200 and optimize an infiltrationpotential of the support element 250 within the preform 200 by spacingout the ceramic particles.

The ceramic fibers are substantially randomly oriented in threedimensions in the preform 200. It is to be appreciated that the termsubstantially means that greater than 90 out of 100 ceramic fibers arerandomly oriented in three dimensions in the preform 200. It is furtherto be appreciated that the term randomly oriented means that adjacentceramic fibers are disposed in different dimensions and that adjacentceramic fibers are free from a pattern of alignment. More specifically,adjacent ceramic fibers oriented in different dimensions are typicallypresent in the preform 200 in an amount of greater than 85 parts byvolume based on 100 parts by volume of the preform 200. Further,adjacent ceramic fibers oriented in the same dimension are typicallypresent in the preform 200 in an amount of from 0.1 to 5 parts by volumebased on 100 parts by volume of the preform 200. Without intending to belimited by theory, it is believed that ceramic fibers substantiallyrandomly oriented in three dimensions provide the preform 200 withuniform strength in three dimensions. As such, the preform 200 of thepresent invention is typically free from fatigue and/or failure in athird, non-reinforced dimension as compared to preform 200 s withceramic fibers oriented in only two dimensions.

The ceramic fibers are typically substantially homogeneously dispersedin the preform 200. It is to be appreciated that the term substantiallymeans greater than 90 out of 100 ceramic fibers in the preform 200 arehomogeneously dispersed in the preform 200. Further, it is to beappreciated that the term homogeneously dispersed means that greaterthan 85% by volume of the ceramic fibers in the preform 200 areuniformly distributed on a scale of twice the diameter of the ceramicfiber. That is, greater than 85 out of 100 ceramic fibers are spaced atleast one ceramic fiber diameter away from an adjacent ceramic fiber.Without intending to be limited by theory, it is believed that ceramicfibers that are substantially homogeneously dispersed in the preform 200provide the preform 200 with uniform density and, consequently, uniformstrength. That is, the preform 200 is typically free from entanglementsand conglomerations of ceramic fibers that cause weak points thattypically decrease strength and stiffness of the preform 200. Since thepreform 200 exhibits uniform density, it is typically unnecessary to addadditional ceramic fibers to the preform 200 after formation to remedyinconsistent density, thereby minimizing production costs of the preform200. Additionally, since the preform 200 of the present invention istypically free from blockages caused by entanglements andconglomerations of ceramic fibers, the preform 200 of the presentinvention also minimizes infiltration blockages caused by entanglementand conglomeration and enables excellent metal infiltration forefficient production of the metal matrix composite.

An uncured preform 200 is typically cured or sintered to form a curedpreform 200, i.e., the preform 200 that has been cured or sintered.During curing or sintering, any liquid components of the uncured preform200 typically burn off, and solids remain in the preform 200. That is,after curing or sintering, solids are typically present in the preform200 in an amount of from 20 to 50 parts by volume based on 100 parts byvolume of the preform 200. Solids are more typically present in thepreform 200 in an amount of from 30 to 40 parts by volume based on 100parts by volume of the preform 200. Air is typically present in thepreform 200 in an amount of from 50 to 80 parts by volume based on 100parts by volume of the preform 200. Air is more typically present in thepreform 200 in an amount of from 60 to 70 parts by volume based on 100parts by volume of the preform 200.

The ceramic fibers are typically present in the uncured preform 200 inan amount of from 5 to 25 parts by weight based on 100 parts by weightof solids in the uncured preform 200. The ceramic fibers typicallyremain as solids in the preform 200 after curing or sintering. That is,the ceramic fibers are typically present in the preform 200 in an amountof from 3 to 15 parts by volume based on 100 parts by volume of thepreform 200. The ceramic fibers are more typically present in thepreform 200 in an amount of from 5 to 10 parts by volume based on 100parts by volume of the preform 200. A specific example of a ceramicfiber is an alumina-silica fiber, commercially available from ThermalCeramics Inc. of Atlanta, Ga.

The ceramic particles typically provide the preform 200 with excellentstiffness and wear resistance and typically comprise an element fromperiod 2, 3, or 4 of the periodic table of the elements. The ceramicparticles more typically comprise an element from period 2 or 3 of theperiodic table of the elements. Typically, the ceramic particlescomprise silicon, oxygen, carbon, aluminum, or boron. The ceramicparticles are typically selected from the group of silicon carbide,alumina, boron carbide, and combinations thereof.

The ceramic particles typically each have a reference dimension of from5 to 50 μm, more typically 5 to 30 μm. One skilled in the art typicallyselects ceramic particles having a reference dimension of from 5 to 10μm, i.e., a smaller ceramic particle, for applications requiring highstrength and stiffness. In contrast, one skilled in the art typicallyselects ceramic particles having a reference dimension of from 10 to 30μm, i.e., a larger ceramic particle, for applications requiring highwear resistance. One skilled in the art typically combines smallerceramic particles and larger ceramic particles for applicationsrequiring high strength, stiffness, and wear resistance.

The ceramic particles are typically present in the uncured preform 200in an amount of from 50 to 75, more typically 60 to 70 parts by weightbased on 100 parts by weight of solids in the uncured preform 200. Theceramic particles typically remain as solids in the preform 200 aftercuring or sintering. That is, the ceramic particles are typicallypresent in the preform 200 in an amount of from 15 to 30 parts by volumebased on 100 parts by volume of the preform 200. The ceramic particlesare more typically present in the preform 200 in an amount of from 22 to28 parts by volume based on 100 parts by volume of the preform 200. Aspecific example of a ceramic particle is silicon carbide, commerciallyavailable from Washington Mills of Niagara Falls, N.Y.

The preform 200 can further comprise a binder component. Withoutintending to be limited by theory, it is believed that the bindercomponent provides the uncured preform 200 with strength. The bindercomponent typically comprises an organic binder and an inorganic binder.More specifically, without intending to be limited by theory, it isbelieved that the organic binder provides an uncured ceramic article,i.e., the uncured preform 200, with strength, whereas the inorganicbinder provides a cured preform 200, i.e., the preform 200, withstrength.

The organic binder of the binder component typically comprises a firstcomponent and a second component. The first component is typically astarch. Without intending to be limited by theory, it is believed thatthe first component provides the uncured preform 200 with strength andreduces adhesion of the second component. The first component istypically present in the uncured preform 200 in an amount of from 1 to10 parts by weight based on 100 parts by weight of solids in the uncuredpreform 200. A specific example of a first component is starch,commercially available as Westar 3+ Cationic Starch from WesbondCorporation of Wilmington, Del.

The second component of the organic binder typically comprises acellulose ether. The cellulose ether typically exhibits reverse thermalgelation and provides lubricity during formation of the uncured preform200. Without intending to be limited by theory, it is believed that thecellulose ether also typically provides surface activity, plasticity,uniform rheology, and uniform distribution of air during formation ofthe uncured preform 200. It is also believed that the cellulose etheralso typically provides the uncured preform 200 with strength. Thecellulose ether is typically selected from the group of methylcellulose, hydroxypropylmethylcellulose, hydroxybutylmethylcellulose,and combinations thereof. The second component is typically present inthe uncured preform 200 in an amount of from 0.5 to 10 parts by weightbased on 100 parts by weight of solids in the uncured preform 200. Asuitable second component is hydroxypropylmethylcellulose, commerciallyavailable under the trade name Methocel™ 4M from The Dow ChemicalCompany of Midland, Mich.

The organic binder is typically present in the uncured preform 200 in anamount of from 0.5 to 25 parts by weight based on 100 parts by weight ofsolids in the uncured preform 200.

The inorganic binder of the binder component is typically silica.Without intending to be limited by theory, it is believed that theinorganic binder provides the preform 200 with strength. The inorganicbinder is typically present in the uncured preform 200 in an amount offrom 2 to 10 parts by weight based on 100 parts by weight of solids inthe uncured preform 200. The inorganic binder typically remains assolids in the preform 200 after curing or sintering. That is, theinorganic binder is typically present in the preform 200 in an amount offrom 2 to 5 parts by volume based on 100 parts by volume of the preform200. A suitable inorganic binder is silica, commercially available underthe trade name Bindzil 1440 Colloidal Silica from Wesbond Corporation ofWilmington, Del.

The binder component is typically present in the uncured preform 200 inan amount of from 5 to 35 parts by weight based on 100 parts by weightof solids in the uncured preform 200.

The uncured preform 200 may further comprise an additive component. Theadditive component typically comprises a filler. One skilled in the arttypically selects the filler to control the density of the preform 200.That is, the filler is typically included in the uncured preform 200according to the weight percent of ceramic particles and ceramic fibersin the uncured preform 200. The filler typically spaces out the ceramicparticles and ceramic fibers to provide the preform 200 with desireddensity and to allow effective metal infiltration during formation ofthe metal matrix composite. The filler may be any filler known in theart. The filler is typically selected to burn off during heating, i.e.,curing or sintering, of the preform 200. The filler is typicallyselected from walnut shell flour, cellulose fiber, air, and combinationsthereof.

The filler is typically present in the uncured preform 200 in an amountof from 0.5 to 20 parts by weight based on 100 parts by weight of solidsin the uncured preform 200. A suitable filler is walnut shell flour,commercially available under from Ecoshell of Corning, Calif.

The additive component may further comprise an air entrainment agent.The air entrainment agent may be any air entrainment agent known in theart that is compatible with the second component of the bindercomponent. One skilled in the art typically selects the air entrainmentagent to increase air bubble content in the preform 200 and stabilizeair bubble size to effect uniform air bubble distribution in the preform200. Without intending to be limited by theory, it is believed that theair entrainment agent decreases surface tension, optimizesdispersability, and contributes to the formation of fine, stable airbubbles to provide the open, porous preform 200 that is receptive tometal infiltration. The air entrainment agent is typically present inthe uncured preform 200 in an amount of from 0.01 to 1 part by weightbased on 100 parts by weight of solids in the uncured preform 200. Asuitable air entrainment agent is commercially available under the tradename Silipon® RN from Hercules of Wilmington, Del.

The additive component may further comprise a surfactant. The surfactantmay be any known surfactant in the art that is compatible with thesecond component of the binder component. One skilled in the arttypically selects the surfactant to lubricate the ceramic fibers andceramic particles. The surfactant is typically present in the uncuredpreform 200 in an amount of from 0.01 to 1 part by weight based on 100parts by weight of solids in the uncured preform 200.

The additive component may further comprise a foam stabilizing agent.The foam stabilizing agent may be any known foam stabilizing agent inthe art that is compatible with the second component of the bindercomponent. One skilled in the art typically selects the foam stabilizingagent to minimize the formation of undesired air bubbles in the uncuredpreform 200. The foam stabilizing agent is typically present in theuncured preform 200 in an amount of from 0.01 to 1 part by weight basedon 100 parts by weight of solids in the uncured preform 200. Theadditive component is typically present in the uncured preform 200 in anamount of from 5 to 30 parts by weight based on 100 parts by weight ofsolids in the uncured preform 200.

The metal matrix composite of the first portion 26 also includes asupport element 250 formed of a metal that impregnates through thepreform 200. The metal is heated to form the molten metal. Inparticular, when the support element 250 is being formed, molten metalencapsulates the outer surface of the preform 200 and impregnates thevoids 275 space of the preform 200. It is to be appreciated that themetal may be a single metal or an alloy. Typically, the metal used inthe manufacturing of the metal matrix composite is selected based on acombination of a strength-to-weight ratio, a thermal conductivity andcost. Generally, a lightweight metal, as compared to the weight of iron,meeting the requirements for yield strength and thermal conductivity isselected.

The yield strength of the metal is typically about 100 to 200 MPa. Thethermal conductivity of the metal is typically about 130 to 180 W/m*K.It is to be appreciated that the values for yield strength and thermalconductivity are all heavily dependent on the metal or the alloy used.The yield strength ranges for cast aluminum are from about 60 to 400MPa, cast magnesium are from about 90 to 150 MPa, and cast titanium arefrom about 700 to 1,100 MPa. The thermal conductivity ranges for castaluminum are from about 100 to 200 W/m*K, cast magnesium are from about50 to 100 W/m*K, and cast titanium are from about 5 to 25 W/m*K. Thecost of the metal is a consideration factored into the selection of themetal used. Typically, the metal is selected from the group of aluminum,magnesium, titanium, and combinations thereof. In one embodiment, themetal comprises aluminum. In another embodiment, the metal consistsessentially of aluminum. In still another embodiment the metal consistsof aluminum.

Once the molten metal impregnates though the preform 200, the innersurface of the preform 200 is defined by both the support element 250and the preform 200 itself. Said differently, the inner surface of thepreform 200 comprises ceramic fibers, ceramic particles and the metal.The inner surface of the preform 200 infiltrated with the supportelement forms the wear surface 125 of the first portion 26. The wearsurface 125 therefore defines the outer disc surface 25 of the firstportion 26. The preform 200 is present on the wear surface 125 in anamount of from about 10 to 60%, more typically about 20 to 50%, and mosttypically about 32 to 38%, based on the surface area of the wear surface125. It is to be appreciated that the preform 200 is uniformlydistributed throughout the surface area of the wear surface 125 of thefirst portion 26. The combination of the metal and the preform 200 ofthe wear surface 125 of the first portion 26 provides excellent strengthand wear resistance at elevated temperatures.

The present invention also relates to a method for forming the firstdisc member 22 and the second disc member 24, and the products formedtherefrom, that expands upon and modifies the procedure for formingmetal matrix composite materials that are described in U.S. Pat. No.8,016,018 to Wood et al. and its copending U.S. patent application Ser.No. 12/174,982, which are herein incorporated by reference. Thedifference between the method described in U.S. Pat. No. 8,016,018 toWood et al. and its copending U.S. patent application Ser. No.12/174,982 and the method for forming the disc members 22, 24 of thepresent application relates first to the shape of the formed preform200, and also to the inclusion of a gap or open area (i.e. an opensection) within the cavity of the mold that does not include the ceramicperform 200. This open section corresponds to the second portion 28 ofthe respective disc members 22, 24.

Thus, the method for forming the first disc member 22, or the seconddisc member 24, includes the step of first extruding a compositioncomprising ceramic particles and ceramic fibers through a multi-screwextruder to form an extrudate, wherein the ceramic fibers are randomlyoriented in three dimensions as the composition is extruded through theextruder. Next, the extrudate is formed to a desired configuration toform a preform 200 comprising the three-dimensional shape of the firstportion of the respective disc member 22, 24. The preform 200 is thenintroduced to a predetermined cavity portion of a mold comprising thethree-dimensional shape of first portion 26 of the respective discmember 22, 24. The rest of the cavity of the mold is shaped tocorrespond to the three dimensional shape of the second portion 28. Themold is closed and a molten metal (i.e. the support element 250) isinjected into the cavity of the mold under pressure. A first portion ofthe molten metal (i.e. of the first support element) infiltrates thepreform 200, while the remainder of the molten material (i.e.corresponding to the the radially inward portion 128 (if utilized) andto a backing portion 228) fills the open section of the cavitycorresponding to the second portion 28 of the respective disc 22, 24.The molten metal is then cooled to form respective first portions 26 andsecond portions 28 of the respective disc member 22, 24, which are thenremoved from the mold and available for use. The outer disc surfaces 25of the first portion 26 of the respective disc member 22, 24 may then bemachined to a final configuration such that ceramic fibers arepositioned along their respective outer wear surface 25.

The invention has been described in an illustrative manner, and it is tobe understood that the terminology which has been used is intended to bein the nature of words of description rather than of limitation. It isnow apparent to those skilled in the art that many modifications andvariations of the present invention are possible in light of the aboveteachings. It is, therefore, to be understood that the invention can bepracticed otherwise than as specifically described.

What is claimed is:
 1. A brake rotor assembly comprising: (a) a firstdisc member having an inner disc surface and an outer disc surface andcomprising: a first preform comprising ceramic particles and ceramicfibers with said first preform having an inner surface and an opposingouter surface and defining a plurality of voids; a first support elementcomprising a metal, a first portion of said first support elementdisposed within said plurality of voids of said first perform betweensaid inner surface and said opposing outer surface of said first preformfor forming a metal matrix composite with said first support elementterminating at said outer surface of said first preform such that saidopposing outer surface of said first preform remains exposed; said firstsupport element further comprising a backing portion extending from saidinner surface of said first preform, said backing portion of said firstsupport element defining at least a portion of said outer disc surfaceof said first disc member; a first wear surface defined by said exposedouter surface and by said first portion of said first support element,said first wear surface defining a portion of said outer disc surface ofsaid first disc member; and (b) a second disc member coupled to saidfirst disc member, said second disc member having an inner disc surfaceand an outer disc surface and comprising: a second preform comprisingceramic particles and ceramic fibers with said second preform having aninner surface and an opposing outer surface and defining a plurality ofvoids; a second support element comprising said metal, a first portionof said second support element disposed within said plurality of voidsof said second perform between said inner surface and said opposingouter surface of said second preform for forming a metal matrixcomposite with said second support element terminating at said opposingouter surface of said second preform such that said opposing outersurface of said second preform remains exposed; said second supportelement further comprising a backing portion extending from said innersurface of said first preform, said backing portion of said secondsupport element defining at least a portion of said outer disc surfaceof said second disc member; a second wear surface defined by saidexposed outer surface and by said first portion of said second supportelement, said second wear surface defining a portion of said outer discsurface of said second disc member; wherein said backing portion of eachof said first support element and said second support element arelocated between said first wear surface and said second wear surfacewhen said first disc member is coupled to said second disc member andwherein said inner disc surface of said first disc member is spacedapart from said second disc member when said first disc member iscoupled to said second disc member.
 2. The brake rotor assembly of claim1, wherein said first support element of said first disc member furthercomprises a radially inward portion extending radially inwardly from aninner periphery of said first preform and from said outer portion, saidradially inward portion of said first support element defining anotherportion of said outer disc surface of said first disc member anddefining another portion of said inner disc surface of said first discmember.
 3. The brake rotor assembly of claim 2, wherein said secondsupport element of said second disc member further comprises a radiallyinward portion extending radially inwardly from an inner periphery ofsaid first preform and from said second portion, said radially inwardportion of said second support element defining another portion of saidouter disc surface of said second disc member and defining anotherportion of said inner disc surface of said second disc member.
 4. Thebrake rotor assembly according to claim 1, wherein said backing portionof said first support element includes a plurality of fins extending ina direction towards said second disc member along said central axis. 5.The brake rotor assembly of claim 4, wherein an end portion of each ofsaid plurality of fins abuts said inner disc surface of said second discmember.
 6. The brake rotor assembly according to claim 1, wherein saidbacking portion of said second support element further comprises aflange extending transverse from said central axis from said outer discsurface and in a direction outwardly away from said second disc member.7. The brake rotor assembly according to claim 1, wherein said backingportion of said first support element includes a plurality of fingersextending in a direction along said central axis towards said seconddisc member to engage a plurality of recesses contained within saidbacking portion of said second support element.
 8. The brake rotorassembly according to claim 3, wherein said backing portion of saidfirst support element includes a plurality of fins extending in adirection along said central axis towards said second disc member; andwherein said radially inward portion of said first support elementincludes a plurality of fingers extending in a direction along saidcentral axis towards said second disc member to engage a plurality ofrecesses contained within said radially inward portion of said secondsupport element.
 9. The brake rotor assembly according to claim 1,wherein said inner disc surface of said backing portion of said firstsupport element includes at least one block portion and wherein saidinner disc surface of said backing portion of said second supportelement includes a corresponding at least one base portion including apost, wherein said post of a respective one of said at least one baseportion is coupled within a slot portion of a corresponding one of saidplurality of base portions to couple said first disc member to saidsecond disc member.
 10. The brake rotor assembly according to claim 9,further comprising a nut coupled to an end of said post to secure saidfirst disc member to said second disc member.
 11. The brake rotorassembly according to claim 1, wherein said first preform is present atsaid first wear surface in an amount of from about 10 to 60 percentbased on a surface area of said first wear surface.
 12. The brake rotorassembly according to claim 1, wherein said first preform is present atsaid first wear surface in an amount of from about 20 to 50 percentbased on a surface area of said first wear surface.
 13. The brake rotorassembly according to claim 1, wherein said first preform is present atsaid at said first wear surface in an amount of from about 32 to 38percent based on a surface area of said first wear surface.
 14. Thebrake rotor assembly according to claim 1, wherein said ceramic fibersof said first preform and said second preform have an aspect ratio ofgreater than 3:1.
 15. The brake rotor assembly according to claim 14,wherein greater than 90 percent of the ceramic fibers of said firstpreform and said second preform are randomly orientated in threedimensions.
 16. The brake rotor assembly according to claim 1, whereinsaid ceramic fibers of said first preform and said second preform areselected from the group of alumina-silica fibers,alumina-silica-zirconia fibers, carbon-graphite fibers, and combinationsthereof.
 17. The brake rotor assembly according to claim 1, wherein saidmetal is selected from the group of aluminum, magnesium, titanium, andcombinations thereof.
 18. The brake rotor assembly according to claim 1,wherein said ceramic particles of said first preform and said secondpreform are selected from the group of elements from period 2, 3, or 4of the periodic table of the elements.